CMake failed: Unknown CMake command "QT5_USE_Modules"

When trying to build spuce, I get the following error:
```
CMake Error at qt_fir/CMakeLists.txt:31 (QT5_USE_Modules):
  Unknown CMake command "QT5_USE_Modules".
```
It seems that `QT5_USE_Modules` has been removed in Qt 5.11.
